Embryonic abnormalities at medical termination of pregnancy with mifepristone and misoprostol during first trimester: observational study.

The availability of new medical techniques for induced abortion in the first trimester enables observation of the incidence and nature of embryonic and fetal abnormalities in early pregnancy. 506 women, presenting to the Liverpool (England) Women's Hospital in 1994-96 for induced abortion before 9 weeks of gestation, were given oral mifepristone followed by oral misoprostol. Fetal tissue was collected from 206 (44%) of these women. Embryos that appeared structurally abnormal on macroscopic evaluation were examined histologically. There were 39 abnormal embryos, including 10 cases of neural tube defect and 6 abdominal wall defects, and a total of 72 potentially nonviable pregnancies. The potential loss rate for embryos with structural abnormalities or other nonviable conditions was 34%--higher than the widely cited 15% rate of spontaneous abortion for clinical pregnancies. The former figure is likely to reflect the true loss rate in early pregnancy.